During a July 2004 project to drill an ice core from the top of Peru's Andes Mountain, the lead researcher took a detour… and made a discovery with profound implications. Learn more.

By analyzing the relics glaciers hold — compacted snow and trapped air from ancient atmospheres, ash from long-quiet volcanoes, dust, insects, and pollen — scientists can reconstruct hundreds of thousands of years of Earth’s climate.

In the past two million years alone, Earth has experienced around 20 ice ages — cycles of advance and retreat of large continental ice sheets. When is the next one due? And will global warming change that due date?

Climate change isn’t always slow, small, and imperceptible in a human lifetime. Ice core analysis has found a single decade in which temperatures over Greenland shot up about 15 degrees Celsius.

Scientists know that the unusual and rapid temperature jump of the Younger Dryas was felt over half the globe. But they're only now beginning to understand why.

Name any debacle of nature, and someone will likely blame it on El Niño. But there’s another large-scale climate pattern that's been overlooked: El Niño's fickle Nordic sister, the North Atlantic Oscillation.

Find out how each NAO phase spins its particular brand of atmospheric tumult, affecting temperature, precipitation, cloudiness, and windiness in different regions — sometimes to drastic ends.

From the chilly depths of the Atlantic to ancient European forests, researchers are combing for data to explain the NAO's mysteries.

Northern Hemispheric temperatures are now at their steamiest. Discover why scientists are concerned about global warming's potential backlash on the NAO.

Where would the world be without oxygen? While it's hard to imagine an Earth without it, for nearly the first half of the planet's 4.5-billion-year history, Earth had no oxygen gas as part of its atmosphere.